Fix email quotations with long lines

When using Vim as your editor of choice, even for email processing - as I do - it is often unpleasing how some email clients quote the email body produced by mailers such as Outlook. The lines often span across multiple visual lines and it's difficult to reply on certain parts of it.

With Vim, you can quickly fix those quotations to maintain a proper hard line break at a desired character width.

First, configure your email client to launch Vim for email replies. For example, when using Mutt, put this line in your .muttrc:

set editor="vim"

Make sure when you have an email message loaded in Vim, that the value of 'formatoptions' contains both c and q, that the value of 'textwidth' is set to a good width (like 76, to insert line breaks after 76 characters), and that 'filetype' is "mail" (technically, what matters is the 'comments' option to be set properly, in particular, it needs to include the n:> flag, which unfortunately the filetype plugin "mail.vim" does not set, but which Vim does include by default).

The bundled mail.vim filetype sets the options 'textwidth' and 'formatoptions' to some reasonable defaults and also defines two maps for quoting text. If these options are not set to your liking, create a file ~/.vim/ftplugin/mail.vim and set them as you like. Assuming your vimrc turns on File type plugins, (e.g. your .vimrc should contain a line like filetype plugin on, see :help ftplugins) this should cause Vim to load your desired settings for any buffer with the "mail" filetype. If your 'comments' option has been changed from the Vim default to no longer include n:>, this file is the place to add it back in as well.

However for mutt, Vim can detect the filetype automatically and therefore load the specific filetype, since the path and filename always contains /tmp/mutt-XXXX where XXX is a variable string. (For other applications, you may need to call Vim and set the filetype specifically like set editor="vim -c 'set filetype=mail'")

Now, when your quoted email is displayed in Vim, there are a few ways to fix the quoted text, all relying on the gq operator:

From visual mode simply press \q (assuming your default Leader key is '\' see :help <LocalLeader>) and the visually selected text will be preceeded by a '> ' using the Mapping provided in the default filetype plugin.